Add basic multi-sim and no-sim support

Changes include
* change format of countries.json & modify other files accordingly
* ask user for mcc/mnc if unknown
* ask user to select sim-card if he has multiple sim-cars

The new format seems more appropriate & flexible, an example being the usage of mccs as keys in the old format (mccs are not guaranteed to be unique per country)
The new format is:
[{"code": iso, "full": fullname, "prefix": +pre, "carriers": {carrier_name: [{"mcc": mcc, "mnc": mnc}, ..], ...}}, ...]
A tool to create this file from a csv-list is added to /tools/create_countries_json.py, and the other files have been changed accordingly.

The user is asked for mcc/mnc if
1. He does not have a sim-card inserted or
2. The selected (or only) sim-card is not associated with the selected country
Fix some minor errors

These errors include:
* Some multi-sim errors
* A language interpolation error
* Some sim-detection errors (required real-phone-testing)
Add some ux & code enhancements

These enhancements include
* Put back-button to top, where it belongs
* A fancier mcc/mnc selection process:
  Carrier is selected first, then mcc/mnc accordingly
* Use 'blur' event-handler instead of 'change'
  Change only fires when the selection is actually changed, not if the user leaves the selection as-is
* Enhanced multi-sim-selection
* Cleaned-up javascipt & fixed jshint errors
* Minor bug fixes
clean-up code & add message for multiple sim-cards

The clean-ups include
* add english message for multiple sim cards
* clear-up and rename js, classes and ids
* reorder the functions in login.js
* add some comments, remove unnecessary console.logs, modify sass sheets to use new ids
correct edge case & apply suggestions; enhance :)

The edge case is that until now, we simply ask the user for mcc/mnc if the selected country does not have the mcc/mnc of the sim. It's probably better to check first whether we have the mcc/mnc combination at all - if we don't; assume the user still wants to use the sim card inserted.
Not knowing the mcc/mnc combination still may not yield best results (e.g. displayed sim cards), but dual-sim + unknown mcc/mnc combination can probably be seen as very unlikely

The following suggestions from @willyaranda have been applied:

* Remove "Welcome to OpenWapp"
* Combine welcome-message 1 & 2
* Remove T&C
* Don't bother users with mcc & mnc at all, if they select a carrier, simply take the first mcc/mnc combination that matches

Additionally, the following enhancements have been made:

* put all found mcc/mnc combinations in a map, so the associated country can be found easily
* don't add an empty country.
* fix error where 'Carrier' was not shown in the carrier selection box before choosing any carrier.
* delete leftovers from mcc/mnc selections; make disabled submit button on init properly
* minor bugfixes; make disabled prefix-selector on confirmation page more clear
* don't use array.from due to support for older versions:
  Navigator.mozMobileConnections started to exist with ffos 1.3 [1], which is based on gecko 28 [2], while array.from started to exist with gecko 32 [3]

[1] https://developer.mozilla.org/en-US/docs/Web/API/Navigator.mozMobileConnections
[2] https://developer.mozilla.org/en-US/Firefox_OS/Releases/1.3
[3] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from#Browser_compatibility
adapt translation
dutch translation
dutch translation updated according to comments of Timmaks
dutch translation, removing 'check' also
fix brakke sentence
Merge pull request #65 from rduivenvoorde/nl2

dutch translation update
Minor update

for gps
Merge pull request #70 from Trynight/patch-7

Minor update
Merge branch 'multi-no-sim' of https://github.com/duesenfranz/openwapp into duesenfranz-multi-no-sim
Updated es after PR #64
Update dependencies
Merge branch 'master' of github.com:mozillahispano/openwapp
1.7.0-rc1
fix double key in dutch translation
minor update for 'it' language