System specification page updates

[lboeman]

Handles a few issues with the system specification page.

• Disables posting of invalid system spec.
• Adds a second "Save System" button as proposed in dashboard review issues #88
• Warns users of existing site with same name instead of allowing them to post and getting a 409 conflict.
• closes Confusing Note about Single Axis #155 Changed warning text about single axis/multiple array to grayed out text for both conditions.
  

[codecov]

Codecov Report

Merging #167 (a919ba3) into main (24492c9) will decrease coverage by 0.00%.
The diff coverage is 87.87%.

@@            Coverage Diff             @@
##             main     #167      +/-   ##
==========================================
- Coverage   88.64%   88.64%   -0.01%     
==========================================
  Files          85       85              
  Lines        3426     3442      +16     
  Branches      289      294       +5     
==========================================
+ Hits         3037     3051      +14     
+ Misses        342      340       -2     
- Partials       47       51       +4     

Flag	Coverage Δ
javascript	77.44% <87.87%> (+0.09%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
dashboard/src/components/model/Array.vue	97.95% <ø> (ø)
dashboard/src/components/model/Arrays.vue	90.00% <ø> (ø)
dashboard/src/components/model/Inverter.vue	77.77% <50.00%> (-3.00%)	⬇️
dashboard/src/components/ModelBase.vue	76.19% <83.33%> (+1.19%)	⬆️
dashboard/src/components/model/System.vue	95.45% <87.50%> (-4.55%)	⬇️
dashboard/src/views/SystemSpec.vue	96.61% <93.75%> (-1.58%)	⬇️
dashboard/src/types/Inverter.ts	100.00% <100.00%> (ø)
dashboard/src/store/mutations.ts	75.00% <0.00%> (+50.00%)	⬆️

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