Created custom sass variable
Removed use of instanceof operator

Fetching and parsing browse entries

Set ip and port by an env variable.

# Conflicts:
#	src/app/app.reducer.ts
#	src/app/core/core.module.ts
#	src/app/shared/shared.module.ts

Mock AdminGuard

For docker containers it would be useful if any configuration variables
defining how to connect to the angular ui and how it connects to the
DSpace 7 REST endpoint could be overriden by environment variables. We
should not extend configuration by environment variables too much.

This PR closes #160