Add XCI, NSP and NCA loading support (#404)

* Add XCI and NCA loading support

* Code style changes

* Add NSP loading

* Changes from code review

* Read XCIs with patches. Code style

* Add KEYS.md file

* Make file extension matching case-insensitive

KEYS.md

@@ -0,0 +1,104 @@
+# Keys
+
+Keys are required for decrypting most of the file formats used by the Nintendo Switch.
+
+Keysets are stored as text files. These 3 filenames are automatically read:  
+`prod.keys` - Contains common keys usedy by all Switch devices.  
+`console.keys` - Contains console-unique keys.  
+`title.keys` - Contains game-specific keys.
+
+Ryujinx will first look for keys in `RyuFS/system`, and if it doesn't find any there it will look in `$HOME/.switch`.
+
+A guide to assist with dumping your own keys can be found [here](https://gist.github.com/roblabla/d8358ab058bbe3b00614740dcba4f208).
+
+## Common keys
+
+Here is a template for a key file containing the main keys Ryujinx uses to read content files.  
+Both `prod.keys` and `console.keys` use this format.
+
+```
+master_key_00                         = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+master_key_01                         = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+master_key_02                         = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+master_key_03                         = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+master_key_04                         = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+master_key_05                         = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+
+titlekek_source                       = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+key_area_key_application_source       = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+key_area_key_ocean_source             = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+key_area_key_system_source            = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+aes_kek_generation_source             = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+aes_key_generation_source             = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+header_kek_source                     = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+header_key_source                     = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+```
+
+## Title keys
+
+Title keys are stored in the format `rights_id,key`.
+
+For example:
+
+```
+01000000000100000000000000000003,XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+01000000000108000000000000000003,XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+01000000000108000000000000000004,XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+```
+
+## Complete key list
+Below is a complete list of keys that are currently recognized.  
+\## represents a hexadecimal number between 00 and 1F  
+@@ represents a hexadecimal number between 00 and 03
+
+### Common keys
+
+```
+master_key_source
+keyblob_mac_key_source
+package2_key_source
+aes_kek_generation_source
+aes_key_generation_source
+key_area_key_application_source
+key_area_key_ocean_source
+key_area_key_system_source
+titlekek_source
+header_kek_source
+header_key_source
+sd_card_kek_source
+sd_card_nca_key_source
+sd_card_save_key_source
+retail_specific_aes_key_source
+per_console_key_source
+bis_kek_source
+bis_key_source_@@
+
+header_key
+xci_header_key
+eticket_rsa_kek
+
+master_key_##
+package1_key_##
+package2_key_##
+titlekek_##
+key_area_key_application_##
+key_area_key_ocean_##
+key_area_key_system_##
+keyblob_key_source_##
+keyblob_##
+```
+
+### Console-unique keys
+
+```
+secure_boot_key
+tsec_key
+device_key
+bis_key_@@
+
+keyblob_key_##
+keyblob_mac_key_##
+encrypted_keyblob_##
+
+sd_seed
+```