Added plugin to provide formatted wiki output

### Overview
The added plugin (wiki.rb) provides two new commands, dokuwiki and mediawiki, which can output database information for the current workspace in wiki formatted text. It accomplishes this by extending Rex::Ui::Text::Table with two new methods (to_dokuwiki and to_mediawiki). Interaction with the plugin is similar to the normal workspace output tools (e.g. hosts, creds, vulns,...)

### Sample Help Menu
```
Usage: dokuwiki <table> [options] [IP1 IP2,IPn]

The first argument must be the type of table to retrieve:
  creds, hosts, loot, services, vulns

OPTIONS:
  -l,--link                Enables links for host addresses
  -n,--namespace <ns>      Changes the default namespace for host links
  -o,--output <file>       Write output to a file
  -p,--port <ports>        Only return results that relate to given ports
  -s,--search <search>     Only show results that match the provided text
  -i,--heading-size <1-6>  Changes the heading size
  -h,--help                Displays this menu
```

### Other notes
* This plugin has been tested against the most recent stable versions of Dokuwiki (blinky) and Mediawiki (1.22.5).
* This plugin passes msftidy checks.
* This plugin should have yard compatible comments for all added classes and methods.