When Piwik config file becomes un-readable, make it clear that the file still exists but is not readable (#10331)

* * In messages, make it more clear whether config file exists and/or is (not) readable
* When the config file exists but is not readable, provide users the choice between making the file readable, or starting a fresh install
* As long as Piwik is not installed, piwik.php should not return 500 when config file is not readable
* Fixes #10283
* UI tests: updated message when config file is not found

* Enforce the Minimum PHP version in composer.json using "platform" feature
Added in https://github.com/composer/composer/commit/a57c51e8d78156612e49dec1c54d3184f260f144

It was found that this flag is very important to use to make sure the package we build and release will be compatible with this PHP version.
Otherwise, the minimum PHP version enforced would be the version where our build script runs, which could be PHP 5.5 or PHP 7 which would have caused serious issues.

* Update doctrine/cache, monolog,piwik/network, piwik/cache, piwik/php-tracker  etc.
https://github.com/piwik/piwik/issues/10058

* Release checklist to check that composer.json is correctly defined

* Use latest travis scripts for https://github.com/piwik/travis-scripts/commit/30d7b16940058a3dcea37dd7e7ed7241090bf57a

* .travis.yml file is out of date, auto-updating .travis.yml file.

* Use latest travis scripts for https://github.com/piwik/travis-scripts/commit/63445cf4a53e6e115a31ecacd79327dc5bfb2494

* .travis.yml file is out of date, auto-updating .travis.yml file.

Submodules including https://github.com/piwik/travis-scripts/pull/28 https://github.com/piwik/piwik/issues/10323

* Display the right message when segment is set to real time

* Correct logic

* UI tests: minor messaging change

[automatic translation update] Updated 54 strings in 7 languages (nl, es, he, pt-br, cs, el, uk)

Update piwik/network component to 0.2.0 release for IPv6 ranges support https://github.com/piwik/piwik/issues/9411 (#10324)

* use log tables to decide which tables can be purged

* make sure to return the number of deleted visits

* fix tests

* added method to get a goal

* always fetch goal directly to not having to iterate over all goals

* added new changelog entry for devs

Adds confirmation when changing segments definition

jslint not working on IE8 it seems

piwik.js: Prepend a slash to all paths such as when users don't specify leading slash for URL path (#10302)

* When a datatable is manipulated in memory, the correct id subtable is stored in metadata and must be fetched from there.

 #10271 #10105