Rename sqlite database location config option to 'path' to match other config

[jacobtomlinson]

I noticed that the sqlite database has a config option file to set where the database is, but other options such as skills use the key path to set where something is.

This PR updates the sqlite database to use path but also includes file as an alias with a deprecation warning.

Status

READY

How Has This Been Tested?

• Updated unit tests to use new path option
• Added unit test for old file option to ensure backward compatibility

Checklist:

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[codecov]

Codecov Report

Merging #1481 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1481   +/-   ##
=======================================
  Coverage   99.90%   99.90%           
=======================================
  Files          52       52           
  Lines        3280     3281    +1     
=======================================
+ Hits         3277     3278    +1     
  Misses          3        3           

Impacted Files	Coverage Δ
opsdroid/database/sqlite/__init__.py	100.00% <100.00%> (ø)

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