FIx minor issues from 2.7.0 rc3

Please place build instruction and supported platforms in the README.
The wiki may change over time and that may make it difficult to build older versions.

I checked:
- name contains incubating
- signatures and hashes correct
- DISCLAIMER exists
- LICENSE seem to be missing a few things
- NOTICE correct
- All ASF files have ASF headers
- One possible binary file that shouldn’t be in the source release? [15] (not sure what this is)
- Couldn’t compile from source. Please include build instructions in the package.

LICENSE is missing
- File [1] has different copyright owner than in LICENSE. Looks to come from a product called Valgrind.
- This file [5] copyright (C) 2011 Jesus Leganes “piranna"
- This BSD licensed file copyright Kitware
- This MIT licensed files [9]. The Cloudera copyright may need to be remove if it was part of 
the software grant?
- MIT license normalise bundled in [13][14]

Couldn't build from source on OSX with this error when running build all.
./buildall.sh  gives:
/apache-impala-incubating-2.7.0/bin/impala-config.sh: line 375: nproc: command not found

The build instruction on the wiki mention OSX is not support that would of been nice to know 
up front. [16]

This files [2][3][4][7] incorrectly (I think) have ASF copyright lines. [8] may also have an issue 
with 2 owners was this part of the original software grant or not?

May also want to fix this [10] the licence of 0.1.1 is unknown [11], but 0.1.3 is Apache licensed.[12]

The last line in LICENSE re JQuery I think can be removed.

Thanks,
Justin

1. ./be/src/gutil/valgrind.h
2. ./fe/src/test/resources/hbase-site.xml.template
3 ./testdata/cluster/node_templates/common/etc/hadoop/conf/hadoop-policy.xml
4. ./testdata/cluster/node_templates/common/etc/hadoop/conf/log4j.properties.tmpl
5. ./apache-impala-incubating-2.7.0/shell/ext-py/sqlparse-0.1.14/sqlparse/pipeline.py
6. ./cmake_modules/FindJNI.cmake
7. ./testdata/cluster/node_templates/common/etc/hadoop/conf/log4j.properties.tmpl
8. ./bin/file2array.sh
9 ./be/src/thirdparty/squeasel/squeasel.?
10. /shell/ext-py/sasl-0.1.1/*
11. https://pypi.python.org/pypi/sasl/0.1.1
12. https://pypi.python.org/pypi/sasl/0.1.3
13. ./tests/comparison/leopard/static/css/bootstrap.css
14. ./www/bootstrap/css/bootstrap.css
15. ./apache-impala-incubating-2.7.0/llvm-ir/test-loop.bc
16 https://cwiki.apache.org/confluence/display/IMPALA/Building+Impala