modified edit schedule dialog to avoid start date in the past

[saberlynx]

• Added a "now" button to help users jump to current date
• Added year dropdown in case users deal with timeframes far from now, to avoid excessive clicking.
• Changed some titles to hopefully make explicit to the user values they're changing

Checklist:

• [] Tests
• CHANGELOG Entry

[codecov]

Codecov Report

Merging #1519 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #1519      +/-   ##
==========================================
- Coverage   37.15%   37.14%   -0.01%     
==========================================
  Files        1001     1001              
  Lines       22330    22335       +5     
  Branches     6143     6143              
==========================================
  Hits         8297     8297              
- Misses      12719    12724       +5     
  Partials     1314     1314

Impacted Files	Coverage Δ
gsa/src/web/pages/schedules/dialog.js	10.23% <0%> (-0.42%)	⬇️

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