FAB-11335 Fix bootstrap.sh args handling
FAB-11335 Fix bootstrap.sh args handling

This change fixes the parsing of the optional arguments and displays a more
accurate usage message:

$ ./scripts/bootstrap.sh -h
Usage: bootstrap.sh [version [ca_version [thirdparty_version]]] [options]

options:
-h : this help
-d : bypass docker image download
-s : bypass fabric-samples repo clone
-b : bypass download of platform-specific binaries

e.g. bootstrap.sh 1.2.0 -s
would download docker images and binaries for version 1.2.0

$ ./scripts/bootstrap.sh 1.2.0 -b

Installing hyperledger/fabric-samples repo

===> Checking out v1.2.0 branch of hyperledger/fabric-samples
HEAD is now at ed81d7b... [FAB-10811] fabric-ca sample is broken on v1.2

Installing Hyperledger Fabric docker images

===> Pulling fabric Images
==> FABRIC IMAGE: peer
...

FAB-11335 #done

Change-Id: I94facb853e7fdbf50e0a6a9eb76358cfee010e3c
Signed-off-by: Arnaud J Le Hors <336b2f4fb14e0a6aba0291ba81894e387297584e@us.ibm.com>

stemlending/fabric,jimthematrix/fabric,manish-sethi/fabric-sidedb,hyperledger/fabric,manish-sethi/fabric,muralisrini/fabric,binhn/fabric,stemlending/fabric,manish-sethi/fabric-sidedb,manish-sethi/fabric-sidedb,hyperledger/fabric,manish-sethi/fabric-sidedb,xixuejia/fabric,xixuejia/fabric,stemlending/fabric,muralisrini/fabric,jimthematrix/fabric,binhn/fabric,manish-sethi/fabric-sidedb,xixuejia/fabric,stemlending/fabric,manish-sethi/fabric,manish-sethi/fabric-sidedb,manish-sethi/fabric-sidedb,binhn/fabric,muralisrini/fabric