set UTF-8 for android update command explicitly

Fix for fail in to update android package. It is happened to meet under the following conditions both.

* User environment is not used UTF-8 in default file.encoding in java
* Android-sdk license text is included not-ASCII code characters.

If user define JAVA_TOOL_OPTIONS in env, inherit it.
fix: logic to compare versions "not installed" with "contain minor"(ex: 20.0.1)

method bulldozer.targets.android.TargetAndroid._install_android_packages()
If build-tools is not installed, then variable "v_build_tools" is string = '0'.
If latest version contains minor version code ~ example 19.0.3 ~, then variable "ver" is list = [19, 0, 3].

In that case, build-tools is not enable to install, because expression([19, 0, 3] > '0') returns False.
Merge pull request #155 from attakei/patches/lock_java_file_encoding

Set "UTF-8" to java file.encoding for android update command explicitly
note about buildozer.io
link
Merge pull request #157 from nickyspag/master

added note about buildozer not having anything to do with buildozer.io
Skip invalid name as version in build-tools directory.(ex: .DS_Store)
delete print for debug
Remove duplicated checkbin()
Merge pull request #156 from attakei/patches/resolve_compare_versions

Fixed logic to compare with “non installed” with “minor version upped"
Merge pull request #160 from attakei/master

Remove duplicated checkbin().
fix build error and allow redirecting build folder

fixes #161 checks if build-tools exists and returns if it does not so it can be fetched
fixes #162 set builddir in you spec file so the packages are created outside your project
builddir = /tmp/buildozer/  # for example
Merge pull request #163 from olymk2/master

fix build error and allow redirecting build folder