Added configurable settings (...)

Settings form, with:
- Entries per page
- FS watching
- Select new files
Bugfixes, known bugs, entry count fixes (...)

- Entry count now refers to VISIBLE entries, rather than ALL entries including invisible onces (eg. group closing without conclusions)
- All these settings show already-existing existing bugs to fix:
  - When an HTML page starts with open groups, these groups increment the left-hand line count, even if not visible.
  - Related: HTML pages starting with open groups aren't shown at all unless these groups contain errors/warnings, or unless the user guesses what the issue is and hits Log Page => Open all groups.
  - Style bug: Fast-forward icons are shown on a whole new line.
  - Open groups are not clickable when they're too long AND expanded.
  - Same for exception lines.
Bugfixes (...)

- Removed count per visible entry, as it conflicts with index (itself using MultiLogReader's ReadFirstPage/NextPage)
JSON generation next to HTML files. (...)

- Prepping for client-based rendering.
Monitor list indexed in monitors.json (fixed).
Using structured entries. (...)

- Moved and refactored JSON writer into SimpleJsonWriter.
JSON fixes.
Merge remote-tracking branch 'benjamin/mon2htm' into develop
3.0.17 (released CKMon2Htm only)