Conda name flag

[KevinMenden]

This PR adds a --conda-name, -c flag to nf-core modules create to allow sidestepping of questionary, e.g. during pytest.

Fixes #988

PR checklist

• This comment contains a description of changes (with reason)
• CHANGELOG.md is updated
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

[codecov]

Codecov Report

Merging #989 (c2ff72e) into dev (21e6b3a) will increase coverage by 0.00%.
The diff coverage is 80.00%.

@@           Coverage Diff           @@
##              dev     #989   +/-   ##
=======================================
  Coverage   69.21%   69.22%           
=======================================
  Files          34       34           
  Lines        4256     4257    +1     
=======================================
+ Hits         2946     2947    +1     
  Misses       1310     1310           

Impacted Files	Coverage Δ
nf_core/__main__.py	61.39% <66.66%> (+0.12%)	⬆️
nf_core/modules/create.py	59.57% <100.00%> (ø)

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[drpatelh]

LGTM @KevinMenden Just a minor comment.