Importing files back into cache

[villermen]

Perfect reverse of CacheBase.Extract.

• Putting files in the cache takes very long sometimes #40 probably needs to be fixed in order to make this actually bearable.
• Library functionality.
• CLI option.

[villermen]

Related to #52.

[villermen]

Sad thing is, at the end of the day the checksums will have to match.
The created cache can thus only be used for private clients...

[villermen]

CLI arguments can be extended quite easily this way:

rsct import --java=dir --files=14,40/1-100