Upgrade to Checkstyle 7.6.1

Bug fixes:

    SummaryJavadoc: need special processing of inheritDoc tag. Author: Sagar #3908
    Indentation check fails for Line Wrapped Anonymous Inner Class with LCurly on newline. Author: Andrew Kuchev #3612
    Regression false-positive FinalLocalVariable. Author: Luolc #3172
    ImportControlLoader does not close InputStream and leaks filehandles when xml is malformed. Author: Giorgos Gaganis #3962
    RightCurly: ALONE option doen't work for a singleline IF. Author: Andrei Selkin #4044
    Test failed due to locale message settings. (with non-English locale settings). Author: Luolc #3896
    Control Characters are not skipped with google_checks config. Author: Luolc #3700
    WhitespaceAfterCheck: problem with multiline typecast. Author: Andrew Kuchev #3850
    try to avoid non jdk runtime exceptions in code. Author: Vladislav Lisetskii #3763

Notes:

    README: broken link. Author: unrealwork #4093
    Wrong German translation of declaration.order.access in messages_de.properties. Author: sirdis #4081
    Perform refactoring of AnnotationLocationCheck to increase code readability. Author: Andrei Selkin #4055
    google_checks: update to most recent version of style guide ( Feb 28, 2017 ). Author: Roman Ivanov #3888
    spelling: fix spelling and punctuation in comments (RightCurly). Author: Andrei Selkin
    google_checks: update to most recent version of style guide (3 November 2016). Author: Andrei Selkin #3755
    NPath for empty block is 1. Author: Roman Ivanov #4045
    Add new setting in Beginning Development for IDEA docs. Author: Vikramaditya Kukreja #4030
    doc: fix typos in Travis PR validation messages. Author: Vladislav Lisetskii
    UTs should not use ROOT locale when they test violation/error message . Author: Luolc #3989
    wercker ci should have most of testing launches on real code to shorten time of Travis execution. Author: Roman Ivanov #3798
    Split and Organize Checkstyle inputs by Test for SeparatorWrap. Author: Sagar #3904
    doc: update documentation for usage of "period" property at SummaryJavadoc . Author: Sagar #3906
    spelling: corrected sentence. Author: Sagar
    EmptyLineSeparator check not enforcing empty line after class def, enum def or interface def tokens. Author: Roman Ivanov #3089
    spelling: change 'suite' to 'suit'. Author: ljacqu
    WritingChecks: add documentation on java grammar. Author: Sagar #3883
    expand documentation on METHOD_REF token. Author: Luolc #3731
    circleci: provide ability to skip CI executions base on commit files. Author: Vladislav Lisetskii #3869
    RequireThisCheck is not fully covered with UTs. Author: Andrei Selkin #3848
    spelling: fix typo in documentation. Author: Craig P. Motlin
    Code coverage is not working for certain classes in checkstyle. Author: Andrei Selkin #3843
    Travis faliure: "sonatype-nexus-staging not found" during release. Author: Roman Ivanov #3868