Check if the List is null before using it

The variable "List<NetAddress> locations" might be null, so we should
check it before using its method size() in case that it throws a
NullPointerException.
Merge pull request #161 from WangTaoTheTonic/master

Check if the List is null before using it
Fixed escaping path names in the webapp

Path names and links needed to be properly escaped
Make parseMemorySize handle PB size

We need to use java BigDecimal to multiply the parsed size with the
petabyte size, since doubles loose precision at that magnitude.
Make comment consistent with the code
Merge pull request #162 from WangTaoTheTonic/master

Make comment consistent with the code
Merge pull request #163 from manugoyal/html-escape-fix

Fixed escaping path names in the webapp
Moved PBDecimal definition to CommonUtils

Since it's only used there.
Cleanups
Merge pull request #164 from manugoyal/handle_pb

Make parseMemorySize handle PB size
Fix deadlock issue in freeBlock
under FS prefix file:// should be treated the same as local FS
Merge pull request #165 from colorant/lock

Fix deadlock issue in freeBlock
Merge pull request #167 from Du-Li/master

under FS prefix file:// should be treated the same as local FS
This commit fixes loadufs command line to take parameters: bin/tachyon loadufs <TachyonPath> <UnderfsPath> [<Optional Excluding Prefixes;>]

(1) It adds a new method UnderfsUtil.getInfo/5 for implementing the new loadufs command line while keeping the old getInfo/4 for compatibility.
(2) It adds toString methods in PrefixList and TachyonFS for printing meaningful debug messages.
(3) It fixes list() in UnderFileSystemSingleLocal to return absolute paths, to be consistent with UnderFileSystemHdfs.
(4) It smooths out the uses of list() in other modules.
(5) It fixes docs/Syncing-the-Underlying-Filesystem.md accordingly.
auto-reformatted for code style
Added methods to CommonUtils

They come in handy across the code base
Fixed CommonUtils.concat check
polishing code style
More fixes to path manipulation functions