Add ability to create backups from command line using existing profiles

[samuel-w]

Syntax:

  --create PROFILE [PROFILE ...]
                        Create a backup in the background using the given profile(s). Vorta must already be running for this to work.

It requires an existing instance of Vorta to be running in the background.

We should not add autocomplete support, since this is meant for use in scripts, not from the command line directly (also it takes extra work and more libraries).

Fixes #364 and sorta kinda #233 and maybe also #438

[codecov-io]

Codecov Report

Merging #556 (05579b2) into master (19b4946) will decrease coverage by 0.50%.
The diff coverage is 26.82%.

@@            Coverage Diff             @@
##           master     #556      +/-   ##
==========================================
- Coverage   74.48%   73.98%   -0.51%     
==========================================
  Files          53       53              
  Lines        3422     3456      +34     
==========================================
+ Hits         2549     2557       +8     
- Misses        873      899      +26     

Impacted Files	Coverage Δ
src/vorta/__main__.py	0.00% <0.00%> (ø)
src/vorta/borg/create.py	48.93% <0.00%> (-0.53%)	⬇️
src/vorta/application.py	57.77% <26.31%> (-11.16%)	⬇️
src/vorta/utils.py	60.86% <100.00%> (+0.21%)	⬆️

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