Add missing checks to vdc, vdcuser and account templates

[katia-e]

• Require state install to be OK in all actions accept install itself.
• Uninstall action always unsets state install.
• In add_user for vdc and account template add check that user was installed.
• Add argument validation in add_user actions: name should be given.

closes: #74

[codecov-io]

Codecov Report

Merging #75 into master will decrease coverage by <1%. The diff coverage is 73%.

@@         Coverage Diff          @@
##           master   #75   +/-   ##
====================================
- Coverage      89%   89%   -1%     
====================================
  Files          10    10           
  Lines         828   837    +9     
====================================
+ Hits          743   745    +2     
- Misses         85    92    +7

Impacted Files	Coverage Δ
templates/vdc/test_vdc.py	93% <ø> (-1%)	:arrow_down:
templates/account/test_account.py	93% <ø> (-1%)	:arrow_down:
templates/vdcuser/test_vdcuser.py	94% <100%> (-1%)	:arrow_down:
templates/vdc/vdc.py	72% <61%> (-2%)	:arrow_down:
templates/account/account.py	88% <83%> (-1%)	:arrow_down:
templates/vdcuser/vdcuser.py	96% <85%> (-2%)	:arrow_down:

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[katia-e]

closes #77

[katia-e]

closes #79