.gitignore: *pyc, *.pyo, python packaging and eclipse cruft
added oaiharvest package
added basic harvesting functionality

1. harvest from a given base URL
2. write to .xml files in specified directory (current directory if
   omitted)

Harvesting supports OAI-PMH parameters:

- metadataPrefix
- from
- until
added requirements file
docs: added README
added setup files
docs: moved LICENSE out to its own file
docs: ReST formatting fixes in README
docs: fixed help for metadataPrefix
add/remove providers in persistent database of providers
added capability to list configured providers
added some restrictions on provider short names
fixed logger inheritance in config.verify_database
increased name length limit, made a module constant
validate added base URLs by fetching `Identify` response
detect duplicate names early (before validating provider)

Attempt to create provider rows before carrying out validation of
other values (base URL, metadata prefix).
validate chosen metadataPrefix is available from provider
+func: added validation of added providers

Merge branch 'feature/validate' into develop
added "all" as reserved provider name
added some logging to harvest module