Add job script submission and generation step

[SeanBryan51]

This change adds a subcommand fluxsite-submit-job that writes the PBS job to the file system and then submits the job to the queue. This allows us to run the full fluxsite test by executing each step separately, i.e. benchcab checkout && benchcab build && benchcab fluxsite-setup-work-dir && benchcab fluxsite-submit-job.

Fixes #109

[codecov[bot]]

Codecov Report

Merging #120 (49da522) into master (b5c1956) will decrease coverage by 0.10%. Report is 1 commits behind head on master. The diff coverage is 71.42%.

@@            Coverage Diff             @@
##           master     #120      +/-   ##
==========================================
- Coverage   88.55%   88.46%   -0.10%     
==========================================
  Files          26       26              
  Lines        1381     1387       +6     
==========================================
+ Hits         1223     1227       +4     
- Misses        158      160       +2     

Files Changed	Coverage Δ
benchcab/benchcab.py	36.70% <0.00%> (-0.48%)	:arrow_down:
benchcab/cli.py	100.00% <100.00%> (ø)
tests/test_cli.py	100.00% <100.00%> (ø)