Editorial updates of documentation QoD_API.md

[hdamker]

After the content update for v0.8.0 with #71 here some editorial fixes within QoD_API.md, also to create a stable base for further updates/PRs:

• Reformated some tables as HTML tables (to get rid of the overlong source code lines which couldn't be reviewed)
• More consistent use of QoD vs QoS
• Consistent use of "QoS session resource" instead "QoS session"
• Consolidated mixed use of "mobile network operator" vs "communication service provider"
• Some further minor typos

Will close #58

NOTE: this PR is not about correcting content issues (like error code etc), these should be raised as issues, especially if also the API definition YAML need to be changed

[hdamker]

@akoshunyadi @shilpa-padgaonkar @eric-murray @jlurien @jpengar @patrice-conil @SylMOREL @tlohmar: would be great if some of you can have a look and approve the changes. Also further suggestions for editorial changes/corrections are welcome.

[jlurien]

@hdamker I see you have just merged this branch. At least we should correct 201 for createSession, other suggestions are more cosmetic

[hdamker]

@jlurien thanks for your comments, will change them within a new PR.