IsoMapPack writing! More map writing. Theaters

- Added parsing and writing of Map section
- Added parsing and writing of SpecialFlags section
- Once Theater key is parsed, the actual Theater control file and
content is parsed
- Basenodes from House are now written as 3 digits instead of 1 (crash
on parsing)
- Fixed parsing of missing base nodes
- Fixed writing of Unit entry string (missed out 2 number values)
- Removed message from FileSystem saying a file doesn't exist, promoted
to individual file type classes