Improve tooltip display

[MikhailArkhipov]

Manual coversion of pydoc to markdown
Fixes #716, #627, #692

[codecov]

Codecov Report

Merging #725 into master will increase coverage by 0.22%.
The diff coverage is 86.7%.

@@            Coverage Diff             @@
##           master     #725      +/-   ##
==========================================
+ Coverage   62.41%   62.63%   +0.22%     
==========================================
  Files         241      242       +1     
  Lines       11113    11236     +123     
  Branches     2002     2033      +31     
==========================================
+ Hits         6936     7038     +102     
- Misses       4169     4190      +21     
  Partials        8        8

Impacted Files	Coverage Δ
src/client/language/tokenizer.ts	85.47% <100%> (ø)	⬆️
src/client/common/markdown/restTextConverter.ts	84.67% <84.67%> (ø)
src/client/providers/itemInfoSource.ts	92.85% <94.28%> (-0.8%)	⬇️

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