Remote SDA launcher

[para2x]

After a series of checks, Using a function called SDA_remote_launcher I copy over all the required files for independently running SDA on remote. Along with the usual requirements for running SDA, I also copy a launcher file called SDA_launcher.R (located in inst/RemoteLauncher) which is responsible for calling the actual SDA function. This function is called through nohup and as a result it creates an output file capturing the progress of the SDA run on remote.
If launcher successfully start the nohup job it will return a folder path on remote as well as a PID corresponding to the SDA job. I will later use another function called Remote_Sync_launcher to launch a nohup syncing job on local monitoring the PID on the remote and syncing the outputs with local.

Description

Motivation and Context

Review Time Estimate

• Immediately
• Within one week
• When possible

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the CHANGELOG.md.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[para2x]

@mdietze this PR is ready for review. I will start writing the documentation as soon as you give me the green light on the implementation.

[mdietze]

In addition to the line-by-line changes, there doesn't seem to be any updates to the general documentation. This is too big of a change / feature addition to not have text explaining how it works and how it's used. In particular, new pecan xml tags definitely have to be documented.

[para2x]

@serbinsh @bailsofhay I don't think I missed any comments. I addressed them all. If you think you don't have any more comments please approve this so I can ask Mike to do the final review.

[para2x]

@mdietze: I addressed @bailsofhay and @serbinsh comments and got their approval on this PR. I know it's a very large PR, but that'd be awesome if you could also give this a look when you have free time.

[mdietze]

In addition to my own requests, there were a lot of reasonable formatting improvements from Shawn that were marked as 'resolved' when they should have been merged in.

[mdietze]

I know this was discussed in a thread somewhere, but remind me why this needs to be done (rather than relying on the GEF to treat this as a true zero)

[para2x]

I think we did that because in line 52-54, few variables are divided by wood_total_C and we didn't want to make NaNs.

[mdietze]

Additional comment: this pull request seems to include the updated to the multi-site options for how Q is structured, but those concepts and settings flags are not included in the documentation. Also, the documentation for running SDA on remote (and enabling Restart) explains the comments, but not the flags that turn these feature on and off.

[araiho]

I'm really excited for this PR. It's awesome that you would be able to run the SDA runs remotely. I was wondering about the different dimensions of Q and if you have simulation scripts that prove that they are working correctly? I know that that has made a big difference for me in the past.