Add get() to htcondor.param if missing

Old versions of condor-python do not have htcondor.param.get(); monkey-patch
htcondor.param if that is the case. This makes the code less repetitive than
using try/except blocks.

Also, "'foo' in htcondor.param" doesn't work in old versions of condor-python
so replace uses of that with htcondor.param.get()
Add last generated time to 02-ce-auth-generated.conf as an attribute (not just comment text)

This allows monitoring systems to keep track of the last generated time.
Add LastCEConfigGenerateTime to COLLECTOR_ATTRS to include it in the collector classad
Merge pull request #34 from matyasselmeci/master

Add get() to htcondor.param if missing