Remove deprecated container manager methods

[stefanoborini]

Removes deprecated functions on the container manager and replaces them with a better interface.

[codecov-io]

Codecov Report

Merging #391 into master will decrease coverage by 0.08%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #391      +/-   ##
==========================================
- Coverage   95.33%   95.24%   -0.09%     
==========================================
  Files          94       94              
  Lines        4010     3998      -12     
  Branches      261      258       -3     
==========================================
- Hits         3823     3808      -15     
- Misses        129      133       +4     
+ Partials       58       57       -1

Impacted Files	Coverage Δ
...eappmanager/docker/tests/test_container_manager.py	100% <100%> (ø)	⬆️
remoteappmanager/webapi/container.py	82.4% <100%> (-0.05%)	⬇️
remoteappmanager/webapi/admin/container.py	90% <100%> (ø)	⬆️
...oteappmanager/webapi/admin/tests/test_container.py	100% <100%> (ø)	⬆️
...oteappmanager/handlers/admin/containers_handler.py	100% <100%> (ø)	⬆️
remoteappmanager/tests/utils.py	92.64% <100%> (+0.1%)	⬆️
remoteappmanager/webapi/tests/test_application.py	100% <100%> (ø)	⬆️
remoteappmanager/docker/container_manager.py	86.17% <100%> (-0.67%)	⬇️
remoteappmanager/webapi/tests/test_container.py	100% <100%> (ø)	⬆️
remoteappmanager/webapi/application.py	100% <100%> (ø)	⬆️
... and 1 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2f87ad8...1c5ff41. Read the comment docs.