Corrected a typo in Tessellator#addQuadraticVertex()

Fixes #2648 - corrected a typo in a5cbb0e2
Fixed error reporting for bez/quad/curve vertices

When user calls bezierVertex()/quadraticVertex()/curveVertex() and does
not call beginShape()/beginShape(POLYGON) before or forgets to specify
first vertex(), proper error message is shown.
Merge pull request #2649 from JakubValtar/shape-fix

Corrected a typo in Tessellator#addQuadraticVertex()
Synchronize initialization of ContributionListing singleton
Updated related references for frameCount and frameRate, per processing/processing-docs#29
Merge pull request #2735 from federicobond/synchronized-singleton

Synchronize initialization of ContributionListing singleton
Added several related references for textSize(), per processing/processing-docs#29
Merge branch 'master' of github.com:processing/processing
Added several related references to PFont and text(), per processing/processing-docs#29
Add language hooks for Contribution Manager
Merge pull request #2737 from federicobond/localize-contrib

Add language hooks for Contribution Manager
Update and rename processing to PDE_tr.properties
Rename PDE_tr.properties to app/src/processing/app/languages/PDE_tr.properties
Merge pull request #2740 from gtitaev/master

Fix Turkish language file
Fix 'examples' window title Language key
Rename a few Korean language keys
Merge pull request #2743 from kazimuth/examplesfix

Fix "examples" language key
todo notes and safer failure when language key missing