Modified default sample size in query.trait.data functions

take.samples() had different default (10^6) than derive.trait()
and derive.traits() (10000). In addition, only the former was ever used.
Cleaned up to avoid future confusion.
Initial commit to address gh-245

Passed build.sh --install --test and my own tests.
Could close gh-245 but please double-check.
Merge branch 'master' of github.com:PecanProject/pecan into gh245_fix
Merge branch 'master' of github.com:PecanProject/pecan
Merge branch 'master' of github.com:jam2767/pecan
Merge branch 'master' of github.com:PecanProject/pecan
Merge pull request #261 from ryankelly-uiuc/gh245_fix

Gh245 fix
Merge branch 'master' of github.com:PecanProject/pecan
fix timestep calculation and lat lon query
rename time dimension to cf compliant name in ameriflux files. fix dimension query in met2model
fixed time variables in metgapfill and met2model.SIPNET
add lubridate to list of dependencies
Merge pull request #277 from jam2767/master

fix time dimension name and met2model.SIPNET