Clean up sequence driver, fix recompile problems

[nddrylliog]

1. The sequence driver should name SourceFolders on the basis of the .use file name if they've been added from .use files, instead of the directory path - because with the current ooc conventions, they're all added as 'source', and that sucks for partial recompialtion
2. The sequence driver should be refactored to have a cleverer flow, and SourceFolder should handle itself checking/recompilation of libraries with or without libcaching (ie. stuffing things in .a static or dynamic libraries)
3. The .cacheinfo file format should be upgraded and documented. It should store the SHA1 or MD5 hash of .ooc files in a SourceFolder
4. When 'use'-ing a library, rock should compile all files in that library and cache them, just for sure - the subsequent compilations will not need to recompile that library at all, unless it has changed (different SHA1/MD5 files)
5. Cases of "recompiling without cleaning but my code changes didn't appear in the new executable" should die.

[nddrylliog]

Closed in branch 95x (used to be named branch issue524).

The short version: the driver/archive/sourcefolder/etc. code is now much cleaner, simpler and easier to understand.

libcaching has been thoroughly debugged and the single main issue remains #541, which has an easy bad fix and a slightly harder good fix. Otherwise, libcaching works fine on Linux, OSX, and Windows, and everything is generally much faster.

[nddrylliog]

Closing now.