Cleanup and documentation improvements in **/*.lisp

* src/conditions.lisp (header): fixed one-line summary
  added class and slot documentation; cleaned up method parameters;
  cleaned up comments
* src/protocol.lisp: likewise
* src/mixins.lisp: likewise
* src/configuration.lisp: likewise
* src/schema.lisp: likewise
* src/conversion.lisp: likewise
* src/macros.lisp: likewise
* src/sources/protocol.lisp: likewise
* src/sources/source-commandline.lisp: likewise
* src/sources/source-environment-variables.lisp: likewise
* src/sources/source-file.lisp: likewise
* src/sources/source-stream.lisp: likewise
* src/sources/source-sequence.lisp: removed; was unused
* src/sources/asdf.lisp: likewise
* test/package.lisp: removed unused testing code
Moved ini syntax into separate system

* src/sources/syntax-ini.lisp: renamed src/sources/{ini ->
  syntax}.lisp
* options.asd (system options): removed file src/sources/ini.lisp
* options-and-parser.ini.asd: new file; contains definition of
  options-and-parser.ini system