Package the application

**Add package creation script (Issue #43)**

To package the application into a zip file, you will need to go to `/scripts/packaging.php`, and wait for 2 seconds.

The script copy all needed files/directories into `build` directory, then generate the file `dist/framadate-version-date.zip`, then delete directory `build`.

See merge request !48

* A new page is available on index, it allows user to send by mail all the polls created by a given mail address

Bug with admin name checking && Step 1 input radio aligment

- Passing from POST to GET some of the admin poll's modification buttons : remove vote, remove column, add column.
- Added create_poll.php a specific css file for the radio buttons aligment.
- Added some args to the poll's URL creation.

See merge request !50

Conflicts:
	app/classes/Framadate/Utils.php

	- Update composer.lock by the way
.

Feature/hidden and private polls

**Added an option for the poll's hidden results**
  - At poll creation, a new checkbox is added to hide the results
  - At poll visualization, results are hidden if option is activated
  - At poll edition by the poll maker, the hidden option can be changed

**Added a new edition option**
  - At poll creation, we can choose between "no user modification" and "all users can modify every vote" like before. But we can now also select "each vote can be modified by its owner"
  - This edition option is also available for the poll maker in the poll administration interface
  - When a user votes with this new option activated, an edition link is displayed to him : only this link can allow the user to modify its vote.
  - This functionality will be useful to create "private polls" later.

**Side work**
  - The token generation is now safer, with fallback to unsafe version if the php functions are not available
  - An anchor is added to the edit link, to scroll down to the current line that the user is editing
  - Commited composer.lock (good practice)
  - Added the root htaccess.txt to keep the CLEAN_URL format updated
  - The Message class can now contain a link (only displayed in studs.php where I needed it)

See merge request !45