Removed -d ( --dir ) method of specifying directory. Instead the directory is now a mandatory argument.
The last specified argument will always be treated as the directory.

Consequently as the argument is now mandatory the current working directory is no longer used as a default
and so it must be specified manually if desired.
Bumped version number
remove unused --dir option in help
Added missing manditory command line option in help message for short options.
Introduced "clean up hooks" which are a family of functions (with prefix unrarall-clean- ) which
can perform different clean up tasks.

The basic code to parse the command line options, verify they are valid and actually execute them (untested) are in place.

unrarall-clean-rar and unrarall-clean-nfo have been implemented but not tested.
All other hooks (except the virtual hooks "none" and "all") have stub code only and need to be implemented and tested.
replace tabs with spaces
bump version number to 0.4.0 due to argument changes
Applied various minor fixes that were originally from another commit.
Fixed error in sed regular expression.
Provide slightly more informative message about extraction success.
Introduced function find-regex-escape() that escapes filenames so that it can be used directly in a regular expression for find. This corrects a bug where regex meta-characters present in filenames are interpreted as meta-characters for the regex instead of literal characters.

Also slightly fixed the use of '.' in the regex too.
Added simple implementation for osx_junk and windows_junk hooks
Provide simple implementation of sample_folders and sample_videos hook. Warning the sample_videos hook
could do some real damage if you had a movie with sample as the prefix (.e.g the movie "sample people")

We need something better but this is a reasonable start.
Removed sfv hook as removing sfv files is already handled by clean-rar
Improved sample_videos hook so it only removes video files that...

* Start with prefix "sample"
* then has zero of more characters of anything
* then the name of the rar file (with extension stripped)
* then a video file extension

This should hopefully prevent accidental deletion of video files that legitimately
start with the word "sample".
Fixed bug in sample_videos hook where find would find the appropriate files but not delete them!
add covers folders clean hook
move to use ${RM} instead of rm in the delete file or folder func
Added information about clean up hooks to HACKING file.
Updated README to contain information about hooks.