Update magpie and docker

[davidcaron]

• update dockerfile to pin dependencies for python 2.7
• update magpie routes
• use pavicsearch without ssl verification when configured as such
• temporary fix for a strange bug where a pywps LiteralInput of type string is u'None' instead of None. Maybe this should also be fixed in pywps, but it seems weird that it hasn't happened elsewhere.
• add configuration for maxsingleinputsize=20mb or else the describe process request would fail with the error: could not convert string to float:

Fixes #50

[davidcaron]

Ah, thanks, I think that explains it, 4.2.2 is installed for some reason.

Edit: Nevermind, pywps.__version__ gives 4.2.2 in pywps 4.2.3