Allow waveform.set() to be called before iocInit()

[MJGaughran]

Fixes #21.

With CGP-182 (944e072), waveform.set() was modified to use the dtype attribute, which is only created after softioc.iocInit() is called.

This change adds a default for dtype, preventing this issue.

[Araneidae]

@thomascobb , didn't realise our CI was so broken! I asked @MJGaughran to make this a pull request so that CI would give it a sanity check ... but that seems to be a bit busted 😞

[Araneidae]

Am happy with this, but will wait for CI to be fixed I guess...

[AlexanderWells-diamond]

PR #20 contains both documentation fixes and fixes for the CI. Once that's merged this should clear up. It's also pending review at the moment.

[thomascobb]

I'll make a couple of docs tweaks to #20 then merge it

[codecov]

Codecov Report

Merging #22 (3dda72c) into master (ee1ba0c) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #22      +/-   ##
==========================================
+ Coverage   82.03%   82.05%   +0.02%     
==========================================
  Files          13       13              
  Lines         796      797       +1     
==========================================
+ Hits          653      654       +1     
  Misses        143      143              

Impacted Files	Coverage Δ
softioc/device.py	74.74% <100.00%> (+0.13%)	⬆️

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[thomascobb]

I added a test too and merged in master