Code cleanup and extensibility preparations

Main changes

Extracted settings, string resources, and cache features to better data structures
- PersistentList to replace message cache and blacklist operations.
- messageutil.py and its functions to replace footer assembly and message reply formatting.
- Moved most strings into relevant dictionaries
- Moved login-info to a dictionary, and use argparse to accept command-line args to take login information. It can still be hard-coded, but it can also be provided only at launch.
Removed unused functions and modules (full list below)
Removed unused imports
Severely altered wikipedia fetching code, but it's much simpler and should be easier to expand upon. Only uses the wikipedia module, no more requests needed.
Added requirements.txt
PEP8-ified most formatting, and idiomized most loops, conditions, exceptions, etc. There are still several things I missed or ignored, but overall I think the code looks a bit better.

New Modules

`PersistentList`

It's not super efficient, but it's reasonable. Could probably do for some in-memory caching features to prevent so many file lookups

`messageutil.py`

I included documentation and examples in this file, since it's radically different from the previous system. I tried to build on the idea of the footer_links list to let the entire footer be defined in that way. I also expanded it to include the PM responses for users being blocked or included, and allow messages to be built on each other.

I also created the start to a system to get the intent of a user's PM or reply, currently 'ignore_user' and 'include_user'.

The three of these systems now work together, and it should be easier to add more user interactions.

File Changes

+ bot_blacklist.txt
+ messageutil.py
+ persistentlist.py
+ requirements.txt
- sentences.py

`bot.py` changes

Renamed some functions to better represent their purpose

Removed unused functions and attributes:

- comment_threshold
- num_sentences
- normal_chars
- media_extensions
- image_extensions
- intro_wikipedia_link
- category_wikipedia_link
- get_thumnail
- locateByName
- enter_bot

Replaced some functions and attributes with features in `messageutil`:

- replace_right
- generate_footer

Replaced some attributes with `persistentlist`:

- get_cache
- input_cache
- check_excluded
- excludeuser
- includeuser
- get_bot_list
- check_bot

msg_cache_file → msg_cache
cache_file → com_cache
user_blacklist_file → user_blacklist
bot_list_file → bot_blacklist

Altered wikipedia fetch functions:

All wikipedia fetch functions entirely rely on the wikipedia module. This means, however, that retrieving extracts with a sentence-cutoff is impossible. Instead, the entire first paragraph of a section is used. Most articles have rather small paragraphs, and in my tests I haven't noticed too much difference to the current /u/WikiTextBot functionality, so I think the readability improvements outweigh that downside. The combined length of get_wikipedia_links and get_wiki_text has dropped from 111 lines to 76, with most of that gain in the duplicate code in get_wiki_text.

kittenswolf / WikiTextBot