HttpInterceptor currently rewrites headers in all requests and sets
Content-Type to application/json. However, there are usecases when the
application needs to pass its own headers or keep the different
Content-type.

This commit changes HttpInterceptor to keep the original headers,
add what it needs (authentication) and if not set 'specific-content-type'
header, it sets the Content-Type to application/json.

Don't rewrite Content-type header in all HTTP requests

The problem was caused by a conversion from JSON to dictionary. In the
end, all JSON values are strings. When original python code checked for
instance of int, it always evaluated to False, anything evaluated as a
string and since there was not a test for role == '0' or similar tests,
it was impossible to properly set roles. By trying to cast the value to
int and test for strings when that fails, we can fix the bug.

This check is useless, it needs just to compare to string and otherwise
return Role.guest

Devel user fix

This breaks the polyfills bundle which now needs extra imports

Bug was caused by setting priviliges on the endpoint and therefore
only admins could edit users. Now it checks only for valid session
and in case of non-admin user it checks if they edit themselves.

Only email, username and password were checked for existence.
Now it uses the User model class

Configurator now uses only one ConfigParser instance and in case
of duplicit entries in configs, the items are overwritten.

Fixes #9

This also remove AppModule is not NgModule error

* devel:
  FE: remove init function before bootstrap and fetch config in HTTP

With the exception of Nemea-Dashboard and Nemea-Supervisor, bootstrap
script is able to set up modules properly (creating symlinks, generating
modules.ts). It also merges any dependency file with lgui base
dependencies. Dependencies are completely optional and you can use only
a subset or even none of them.

Warning was printed but skip did not really occur.

User is not inputting old password to update form

* 'move-modules' of https://github.com/CESNET/liberouter-gui:
  Remove example python code

Modularize the Whole LGUI

…into auth-flow

* 'auth-flow' of https://github.com/CESNET/liberouter-gui:
  Users: split user and session info

If some of the requirements files did not end with a newline, it could
cause a problem. Fixed now

#28 Bootstrap: Fix requirements file generation

#27 Authorization Flow

* Fix CESNET/Nemea-Dashboard#9
* Fix #32 in NEMEA Dashboard and NEMEA Configuration

NEMEA Dashboard: CESNET/Nemea-Dashboard@b723aec

Fix #32

* master: