fix/1053_esm_runscripts_argument-start_date

[nwieters]

This PR will read in the current date from command line argument -s (--start_date) if given instead of reading it from the date file.

closes #1053

New functionality:

• Will read the current_date and run_number from the argument given by -s and -r
• Will read *.date file if no argument for current_date (-s) is given
• If current_date is given by argument -s and is different compared to the date in *.date file, it will ask the user to choose which date should be taken.

But:

• current_date date and run_number needs to be set correctly by user if given as arguments -s and -r
  • Check if there is a log file logging the date together with run_number
• When is *.date file written? In maybe_resubmit
• Can a single jobtype be executed on its wown? E.g. only tidy? Or will it continue the simulation because of current resubmit mechanism?

[nwieters]

This is not ready yet, because I want to let the user confirm that the current date should be taken from the argument instead of read in from date file.
The problem I see here is that the experiment will be in some kine of detached state, when using a different date. But on the other hand, if you give -s as argument, you should know what you do. But I think a user note and maybe also a confirmation is good to have.

[mandresm]

Work in progress, to be continued/reviewed by @mandresm

TODO

• File-registry mapping dates to runs
• Run number supported as well