Pyctr

* Fix loading RomFS from a filename in `RomFSReader`
* Fix loading ExeFS from a filename in `ExeFSReader`

* Support loading a decrypted titlekey for `CDNReader`
* Remove unused `sections` attribute from `CDNReader`
* Add `available_sections` to `CDNReader` to provide a list of sections available in the title
* Add `__author__`, `__copyright__`, `__license__`, `__version__`, and `version_info` to `pyctr.__init__`

* Fix endianness issue when converting a `TitleMetadataReader` object to `bytes`

* Don't assume a Cygwin environment is Windows
* Change keyslot for New 3DS key sector keys from 0x11 to 0x43
* This adds a new Keyslot enum item: `Keyslot.New3DSKeySector`
* Document more methods in pyctr.crypto.engine
* Add new `fileio.CloseWrapper` class to provide access to a file object while preventing closing it directly
* Use `CloseWrapper` in `CDNReader.open_raw_section`

* Support NCCH contents with fixed crypto key (zerokey and fixed system key)
* CryptoEngine adds these to fake keyslots 0x41 and 0x42 respectively.
* Fixed setting up keyslot 0x11, used for decrypting the New 3DS key sector

* Add DISA/DIFF reading and writing under `pyctr.type.save`
* This does NOT include Inner FAT support yet.
* This can read and write to IVFC level 4. For now, external tools can be used to read or write to the Inner FAT.
* Add CDN reading under `pyctr.type.cdn`
* Add more docstrings to various modules
* Add seed parameters to ncch, cia, and cdn
* Rename `Keyslot.UDSLocalWAN` to `Keyslot.UDSLocalWLAN`
* Many other internal changes done months ago