BibHarvest: OAI harvesting bug fixes

• Fixed bug that would prevent harvesting of multiple repositories at once (file with harvested data being overwritten by harvesting of next repository... Thanks to Sergio Laberer for having pointed out the problem and helped solving it).

• Improved parsing of input parameter '--repository' when used with (double-)quotes.

• Fixed wrong help documentation wrt '--repository' parameter.

• Fixed bug when calling bibupload with harvested data (when harvesting multiple repositories at once, each harvested repository being bibuploaded again with the next ones; due to "mutable defaults trap" with 'mode' param of 'call_bibupload(..)' function).

• Backported from 50a211189b9fc6758f487b882d8934f5f7a25be9.