Add Objectify filter when creating new projects

[chanseokoh]

Fixes #3076

The filter is needed for both Objectify 5 and 6. The filter covers all incoming URLs (/*).

• Standard Java 7: <filter> and <filter-mapping> in web.xml
• Standard Java 8 and Flexible: new ObjectifyWebFilter class with the @WebFilter annotation (no change in web.xml)

[codecov]

Codecov Report

Merging #3123 into master will increase coverage by 0.2%.
The diff coverage is 95.45%.

@@             Coverage Diff             @@
##             master    #3123     +/-   ##
===========================================
+ Coverage     69.24%   69.44%   +0.2%     
- Complexity     2843     2870     +27     
===========================================
  Files           371      371             
  Lines         13219    13284     +65     
  Branches       1571     1580      +9     
===========================================
+ Hits           9153     9225     +72     
+ Misses         3423     3413     -10     
- Partials        643      646      +3

Impacted Files	Coverage Δ	Complexity Δ
...ets/ui/navigator/model/AppEngineWebDescriptor.java	85.71% <ø> (ø)	3 <0> (ø)	⬇️
...com/google/cloud/tools/eclipse/util/Templates.java	81.81% <ø> (ø)	4 <0> (ø)	⬇️
...clipse/appengine/deploy/CloudSdkStagingHelper.java	88% <0%> (ø)	3 <0> (ø)	⬇️
...ls/eclipse/appengine/newproject/CodeTemplates.java	93.91% <100%> (+0.57%)	30 <11> (+9)	⬆️
...d/tools/eclipse/appengine/ui/AppEngineRuntime.java	100% <100%> (ø)	4 <0> (ø)	⬇️
...tools/eclipse/appengine/facets/WebProjectUtil.java	77.33% <0%> (-1.34%)	27% <0%> (-1%)
...oud/tools/eclipse/swtbot/SwtBotProjectActions.java	29.26% <0%> (-1.22%)	16% <0%> (+6%)
...ow/ui/preferences/RunOptionsDefaultsComponent.java	77.95% <0%> (-0.63%)	58% <0%> (-1%)
...e/cloud/tools/eclipse/util/jobs/FuturisticJob.java	80% <0%> (+1.25%)	29% <0%> (+2%)	⬆️
...d/tools/eclipse/appengine/libraries/BuildPath.java	73.33% <0%> (+2.66%)	22% <0%> (ø)	⬇️
... and 5 more

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[chanseokoh]

Oops, this doesn't work for flex projects. I'll look into it.