Updated Makefile and manuals, new manual added
DOC and Makefile updated to version 0.2.6
Hiding and commenting functionality back in main `Properties` class,
small refactoring of unit tests.
Small cleanup in code
`Engine.LineParser` contains `iscomment()`, `linehaskey()`,
`getlinekey()` and `getlinevalue()`
`getre()` removed, `sets()` will raise DeprecationError if **kwargs is
used