update 1.8 release stuff

update readme; don't await loading of root node

fox extra attribute range display

update license

update examples and readme; polishing & minor fixes

Merge pull request potree#492 from potree/develop

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Merge pull request potree#359 from potree/develop

fix some bugs; update examples

Merge pull request potree#290 from potree/develop

Develop

remove 1.4RC example

Merge pull request potree#173 from potree/develop

Develop