Remove code that produces NPE

Remove code that produces NPE

Export linked files
Don't replace existings

Create new Action for exporting files
TODO: Add to menu

Move to Tools entry

try around with some background task stuf

remove compile errro

Add Progessbar dialog
Add localization

Fix checkstyle

extract to inner class
Add some more output messages
renamed variables

Fix gui display

Fix localization to copy files

Avoid code duplicaiton

* upstream/master:
  Set WM_CLASS to org-jabref-JabRefMain (#3273)
  Terminate JavaFX thread when running with "nogui" option (#3274)

* upstream/master:
  Update gradle to 4.2.1 (#3322)
  Avoid recreation of the EntryEditor (#3187)
  Fix #3133 telemetry by locking azure to 1.0.9
  German translation for missing properties (#3312)
  Improvement for Java FX font rendering on Linux (#3305)
  Add also conversion for em dash
  Add \textendash to the html conversion table
  Update latex2tunicode from 0.2.1 -> 0.2.2
  Added note about updating controlsfx
  Fix exception/freezing on EntryChangedEvent in Entry Editor (#3299)
  Update libs (#3300)
  update guava from 23.0 -> 23.2
  update mvvmfx-validation from 1.6.0 -> 1.7.0
  Resolves #3255 file open dialog should have "supported formates" filetype
  Fix #3235: remote metadata is updated instead of delete + insert (#3282)
  Change OO paths to Libre Office in preferences (#3287)
  Fix #2471: remove line breaks from abstracts in ADS fetcher (#3285)
  Resolves #3280 Empty String instead of N/A (#3288)

Reorder columns
Fix translation error

remove sys out

* upstream/master:
  Small fix in drag and drop handler of linked files (#3328)
  Fix NPE in MainTable (#3318)
  Increase relative size of abstract field in editor (#3320)

Use Task instead of Service
Use CellValueFactory

* upstream/master:
  Change integrity message for names depending on database mode (#3330)
  Fix location bundle with fast access (#3327)
  Small code cleanup
  Fix "path not found" exception

# Conflicts:
#	src/main/java/org/jabref/logic/l10n/Localization.java

Switch gui to border pane
add tooltip to factory

* upstream/master:
  Initializing EntryEditor Tabs on focus (#3331)
  Fix #3292: annotations are now automatically refreshed (#3325)

# Conflicts:
#	CHANGELOG.md

* upstream/master:
  Fix NPE when calling with bib file as cmd argument (#3343)
  update mockito-core from 2.10.0 -> 2.11.0 (#3338)
  Remove underscore in Localized messages (#3336)
  Localisation: French: new entries translated (#3337)
  Refactoring: Lazy init of all editor tabs (#3333)

Add timestamp
Improve GUI

* upstream/master:
  Rework AutoSetFileLinks (#3368)
  revert wrongly commited changes
  Refactorings (#3370)
  Fix freezing when running cleanup file operations like rename (#3315)
  This additional style setting for IDEA (#3355)
  Fix checkstyle
  Add proper equals to content selector
  Source tab entry duplication (#3360)
  Use CITE_COMMENT not only for external latex editors but also for cop… (#3351)
  Updating with new translations (#3348)
  Upgrade error-prone (#3350)
  Jabref_pt_BR partially updated (#3349)
  Delete unused code
  Extract difference finder from gui to logic
  Used late initialization for context menus (#3340)
  Remove unnecessary EntrySorter
  Move existing code to gui and rename change classes to view model
  Small code improvements

…ortPdf

* 'exportPdf' of https://github.com/JabRef/jabref:
  Rename l10n Add timestamp Improve GUI