docs: revise adding components with info about platform-tools

<p>For example, there may be a dependency between the ADT Plugin for Eclipse and

the SDK Tools component. When you install the SDK Tools

component, you would then need to upgrade to the required version of ADT (if you

are developing in Eclipse). In this case, you would find dependencies listed in

"Revisions" section of the <a href="{@docRoot}sdk/eclipse-adt.html#notes">ADT

Plugin Notes</a> and <a href="{@docRoot}sdk/tools-notes.html#notes">SDK Tools

Notes</a> documents. </p>

<p>Additionally, the development tools will notify you with debug warnings

if there is dependency that you need to address. </p>

component, you should also upgrade to the required version of ADT (if you

are developing in Eclipse). In this case,  the major version number for your ADT plugin should

always match the revision number of your SDK Tools (for example, ADT 8.x requires SDK Tools r8).

</p>

<p>Also make sure that, each time you install a new version of the Android platform, you have

the latest version of the SDK Platform-tools component. The SDK Platform-tools contain

tools that are backward compatible with all versions of the Android platform and are

often updated to support new features in the latest version of the Android platform.</p>

<p>The development tools will notify you with debug warnings if there is dependency that you need to

address. The SDK and AVD Manager also enforces dependencies by requiring that you download any

components that are needed by those you have selected.</p>

<h2 id="AddingSites">Adding New Sites</h2>