Prepare #904: Improve the people invite screens

- Rename `ContactPickerViewController` with `HomePeopleSearchViewController`.
- Define a basic view controller class `ContactsTableViewController` to display/filter a contacts list.
- Make `StartChatViewController` inherit of this new class `ContactsTableViewController` to handle contact invite.

Vector/ViewController/ContactsTableViewController.h

@@ -0,0 +1,68 @@
+/*
+ Copyright 2017 OpenMarket Ltd
+ 
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+ 
+ http://www.apache.org/licenses/LICENSE-2.0
+ 
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+#import <MatrixKit/MatrixKit.h>
+
+#import "ContactTableViewCell.h"
+#import "VectorDesignValues.h"
+
+/**
+ 'ContactsTableViewController' instance is used to display/filter a list of contacts.
+ See 'ContactsTableViewController-inherited' object for example of use.
+ */
+@interface ContactsTableViewController : MXKViewController <UITableViewDelegate, UITableViewDataSource>
+{
+@protected
+    // Section indexes
+    NSInteger searchInputSection;
+    NSInteger filteredLocalContactsSection;
+    NSInteger filteredMatrixContactsSection;
+    
+    // The contact used to describe the current user.
+    MXKContact *userContact;
+    
+    // The dictionary of the ignored local contacts, the keys are their email. Empty by default.
+    NSMutableDictionary<NSString*, MXKContact*> *ignoredContactsByEmail;
+    
+    //The dictionary of the ignored matrix contacts, the keys are their matrix identifier. Empty by default.
+    NSMutableDictionary<NSString*, MXKContact*> *ignoredContactsByMatrixId;
+    
+    // Search results
+    NSString *currentSearchText;
+    NSMutableArray<MXKContact*> *filteredLocalContacts;
+    NSMutableArray<MXKContact*> *filteredMatrixContacts;
+    
+    MXKAlert *currentAlert;
+}
+
+@property (weak, nonatomic) IBOutlet UITableView *tableView;
+
+/**
+ Filter the contacts list, by keeping only the contacts who have the search pattern
+ as prefix in their display name, their matrix identifiers and/or their contact methods (emails, phones).
+ 
+ @param searchText the search pattern (nil to reset filtering).
+ @param forceRefresh tell whether the previous filtered contacts list must be reinitialized before searching (use NO by default).
+ */
+- (void)searchWithPattern:(NSString *)searchText forceRefresh:(BOOL)forceRefresh;
+
+/**
+ Refresh the contacts table display.
+ */
+- (void)refreshTableView;
+
+@end
+