WebUI: make API locale independet

Sizes are now given in bytes.
Dates are Unix timestamps and converted to ISO 8601 in the web UI.
Numbers are not converted to strings.
-1 is returned for undefined values.

Some keys have been splitted:

Torrent list (json/torrents)
 * num_seeds: Torrent seeds connected to
 * num_complete: Torrent seeds in the swarm
 * num_leechs: Torrent leechers connected to
 * num_incomplete: Torrent leechers in the swarm

Torrent generic properties (propertiesGeneral/hash)
 * total_uploaded: Total data uploaded
 * total_uploaded_session: Total data uploaded this session
 * total_downloaded: Total data dowloaded
 * total_downloaded_session: Total data downloaded this session
 * time_elapsed: Torrent elapsed time
 * seeding_time: Torrent elapsed time while complete
 * nb_connections: Torrent connection count
 * nb_connections_limit: Torrent connection count limit

Global transfer info (json/transferInfo)
 * dl_info_speed: Global downalod rate
 * dl_info_data: Data downloaded this session
 * up_info_speed: Global upload rate
 * up_info_data: Data uploaded this session

Closes #1524.
Remove unneeded parameters from helper functions for WebUI
Use raw data to sort columns

Store the raw data retrieved in a new data-raw attribute and use
these to sort the columns.

In addition, make the ETA column sortable.
Use localeCompare to sort torrent list by name
Merge pull request #2145 from pmzqla/webui

Make Web API locale independent
Implement episode filter for rss downloader
Add tooltip to episode filter text edit
Fix missing icon for open action in file list
Fix configure script when running with dash

`test 1 == 1` will fail using dash as the default shell. The `test 1 = 1`
syntax works in both Bash and Dash.
Merge pull request #2156 from jleclanche/master

Fix configure script when running with dash
Reduce the number of torrent_handle::torrent_file() calls in QTorrentHandle::prioritize_files(). Closes #2161.

It was reported (#2161) that enabling/disabling a downloading of a file
is considerably slow on libtorrent 1.0.3, but not on 0.16.x. The problem
is that a function torrent_file() in libttorrent 1.0.3 does a deep copy
of torrent_info, while get_torrent_info() in libtorrent 0.16.x only
returns a reference.
Merge pull request #2163 from sorokin/optimize-prioritize-files

Reduce the number of torrent_handle::torrent_file() calls in QTorrentHandle::prioritize_files()
Merge pull request #800 from Gelmir/smart_ep

Implement episode filter for rss downloader
Set placeholder text to torrent content filter.

In commit afb03725ad8fcf6eb1db305bdc89391a573f5968 it was implemented
for torrent list filter. Now it is here for files filter.
Documenting the project's coding guidelines. Closes #2091.
Set piece size to (max) 4Mb instead of empty string when created torrent
is very large.
Fix emptying of piece size combobox when user checks "auto" checkbox.

The function computePathSize returns -1 if file isn't found, not 0.
Merge pull request #2173 from sorokin/placeholder-text-torrent-list

Set placeholder text to torrent content filter.
Merge pull request #2174 from sorokin/fix-empty-combobox

Fix emptying of 'piece size' combobox when user enable 'auto' checkbox and no files are selected
Implement open & select file in file manager [Windows only]