Intro user doc update

Rewritten-docs.md

@@ -1754,17 +1754,24 @@ modern web applications.
 
 # User documentation
 
-Users interact with the ReCodEx through the web application. For the best user
-experience we strongly recommend to use modern web browsers with enabled `CSS`
-and mostly `Javascript`. Another features which are necessary to proper work
-with application are `Cookies` and browser `Local storage`.
+Users interact with the ReCodEx through the web application. It is required to
+use a modern web browser with good HTML5 and CSS3 support. Among others cookies
+and local storage are used. Also a decent JavaScript runtime must be provided by
+the browser.
 
 Supported and tested browsers are: Firefox 50+, Chrome 55+, Opera 42+ and Edge
-13+. Mobile devices are not officially supported and it is possible that
-application will not work properly there.
+13+. Mobile devices often have problems with internalization and possibly lack
+support for some common features of desktop browsers. For us in this stage of
+development is not possible to fine tune the interface for major mobile browsers
+on all mobile platforms. However, it is confirmed to work with latest Google
+Chrome and Gello browser on Android 7.1+. There are reported some issues with
+Firefox which may be fixed in future. Currently there are no data for iOS as
+nobody of us uses Apple devices.
 
 Usage of the web application is divided into the sections concerning the
 particular user roles. Under these sections all possible use cases can be found.
+These sections are inclusive, so more privileged users need to know stuff from
+all less or equal privileged sections than their level of privilege.
 Described roles are:
 
 - Student
@@ -1774,7 +1781,7 @@ Described roles are:
 
 ## Terminology
 
-**Instance** -- Represents a university, company or some other organizational
+**Instance** -- Represents a university, company or some other organization
 unit. Multiple instances can exist in a single ReCodEx installation.
 
 **Group** -- A group of students to which exercises are assigned by a
@@ -1783,8 +1790,8 @@ supervisor. It should typically correspond with a real world lab group.
 **User** -- A person that interacts with the system using the web interface (or
 an alternative client).
 
-**Student** -- A user who is subscribed to some groups and submits solutions to
-exercise assignments.
+**Student** -- A user with least privileges who is subscribed to some groups and
+submits solutions to exercise assignments.
 
 **Supervisor** -- A person responsible for assigning exercises to a group and
 reviewing submissions.