rework email validation regex

[sotanodroid]

There is a couple of emails that I found invalid but Schematics validator passed them as OK.
Examples are: with/slash@gmail.com, ivan.***@mail.ru, d|vor@mail.ru

Symbols | / and ' are commonly used delimiters and many services such as Gmail not allowing them

Changed: email validation regex
Add: unittests

[codecov-commenter]

Codecov Report

Merging #612 into master will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #612   +/-   ##
=======================================
  Coverage   91.06%   91.06%           
=======================================
  Files          24       24           
  Lines        2541     2541           
=======================================
  Hits         2314     2314           
  Misses        227      227           

Impacted Files	Coverage Δ
schematics/types/net.py	93.89% <100.00%> (ø)

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