Create DataTable for viewing Variable

VariableTable works for OceanSITES files, but maybe needs to be made
more general, Maybe StructureTable was supposed to do this, but could
not figure how to get it to work with a Variable.

minor fix to VariablePlot
Merge pull request #77 from petejan/4.5.4

Create DataTable for viewing Variable
Some HTTP servers (i.e. TDS) a 0 value for Content-Length header.

This commit guess the real value for the URL size, making a request with
a range.

Conflicts:
	cdm/src/main/java/ucar/unidata/io/http/HTTPRandomAccessFile.java
fix broken merge in HttpRaf
remove debug in OpendapServlet;
remove failing test
Trying pulling a tarball of maven artifacts.
Set the language as Java in the .travis.yml
Don't build NetCDF for testing, just use a package.

Will replace the old 4.1 package from Ubuntu with another package soon.
Update Travis build badge.
Fixed Gradle's Javadoc generation on JDK8.
* Added a reminder to release.txt to update file permissions.
Merge branch '4.5.4' of https://github.com/Unidata/thredds into 4.5.4